Metallic film for use with storage-battery electrodes and process of preparing the same.



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THOMAS A. EDISON, OF LLEWELLYN PARK, ORANGE, NEW JERSEY, ASSIGNOR TOEDISON STORAGE BATTERY COMPANY, OF WEST ORANGE, NEW JERSEY, CORPORATIONOF NEW JERSEY.

METALLIC FILM FOR USE WITH STORAGE-BATTERY ELECTRODES AND PROCESS OFPREPARING Tm SAllIE. I

Specification of Letters Patent.

Patented Aug. 25, 1908.

Application filed February 6, 1908. Serial No, 414,576.

T 0 all whom it may concern:

Be it known that I, THOMAS ALVA Enrsox, a citizen of the United States,residing at Llewellyn Park, Orange, county of Essex, and State of NewJersey, have invented certain new and useful Improvements in MetallicFilms for Use with Storage-Battery Electrodes and Processes of Preparingthe Same, of which the following is a description.

In the make-up of electrodes. for my improved storage batteries, I haveproposed the cm loymcnt for addition to the active matcria of very thinflakes or scales of a metal which would not be affected, at least to anobjectionable extent, by electrolysis in the alkaline solution, such asnickel or cobalt, or an alloy of the two. Such films are preferably madeby electroplating a series of thin deposits on a suitable cathode, thefilms being separated by alternate dc osits of a soluble metal which canbe later issolved so as to free the nickel or cobalt films. Twodifiiculties have been encounteredin actual practice in connection withthe manufacture of such films which it is the object of the presentinvention to overcome. In the first place, I find that when the filmsareproduced )y electroplating they present smooth and relativelypolished surfaces, to which the particles of active material, such asnickel hydroxid, are enabled to adhere with very little tenacity, evenwhen the particles are compressed into contact with the films underenormous pressure. Consequently, when any internal movement of theactiveparticles within the electrode mass takes place, such as may be due tothe charging and discharging operations or to gas pressure, or to othercauses, opportunity exists for the active particles to separate from thefilms so as to thereby deteriorate the contact conditions within themass. In the second place, I find that while under the perfectconditions of a laboratory experiment, nickel or cobalt, or

other metallic films can be obtained which will be practically free ofany impurity, yet, under commercial conditions where the films arc to bemade in large quantities, it is practically impossible to prevent theintroduction of impurities which will do harm when used for batterywork. The impurities which I have principally encountered in thisconnection have been iron and arsenic,

the presence of which tend to result in the formation of objectionableoxids on the surface of the films, after the electrodes have plaininghow my invention is carried into effect, I will consider iron andarsenic asthe only impurities which are to be expected, but it will beunderstood of course that if other impurities are encountered, thetreatment may be suitably modified to eliminate them without departingfrom the spirit of the invention.

In carrying the invention into effect, I first secure the metal films byany suitable process, preferably by electrodeposition, and I preferablyreduce them to the desired size for actual use, although it will beunderstood that the films may be in relatively large sheets or longstrips and be cut up into the ultimate size after treatment. The filmsarepreferably composed of metallic nickel on account of its cheapness,but other metals may be used, such as cobalt or an alloy of nickel andcobalt. The-films are noW subjected to an oxidizing operation, by whichan oxidation will take place, penetrating a very slight dis tance belowthe surface. This oxidation is effected in any suitable way, such as byheating the films in, an oxidizing atmosphere. The eifect of theoxidation is not only to oxidize the surface particles of the metallicfilms, but also to oxidize the metallic impuri- I to an acid treatment,which will have the subjected to a mixture of nitric and hydrochloricacids in dilute solutions. The treatment described does notobjectionably affect the metallic nickel or cobalt surface of the films,since the iron or arsenic is much more soluble in the dilute acid thanthe nickel or cobalt which will be only slightly attacked. By thusoxidising and then reducing the surfaces of the films, the shiny andpolished effect will be removed, and the films will oartake of a dull ormatted appearance. Un er the microscope, the surfaces thus treatedappear to be pitted with innumerable excessively minuts irregularities,the effect of which when the active'material is tightly compressed intocontact with the films, is to enormously increase theadhe'sion betweenthe same, so that when used in the make-up of a storage batteryelectrode, the intimate contact between-the active particles and thefilms will be always maintained, notwithstanding internal movement. Inother words, the effect is somewhat the same as the great adhesivenessof a label on aroughened glass surface, compared with its ready tendencyto pull off of a smooth surface.

It will, of course, be understood thatwhen the films are sufficientlypure, and when no objectionable amount of impurities exist the specialtreatment for removing the impurities may be dis ensed with, in whichcase the process Wil comprise the reliminary treatment of the films byan oxi izing a cut and the subsequent reduction of the .oxi s so formedto the metallic state.

Having now described my invention, what "I claim as new and desire tosecure by Letters Patent is as follows 1. Insoluble metallic films foradmixture with the active material of storage batteries,

purposes set forth.

with the active material of storage batteries having minutely roughenedor matted surfaces, substantially as and for the purposes set forth.

3. The process of treating insoluble metallic films for admixture withthe active material of storage batteries, which consists in subjectingthe films to a surface oxidation, and in afterwards reducing the oxid soformed to the metallic state, substantially as and for the purposes setforth.

.4. The process of treating insolublemetallic films for 'admixture.,withthe active material of storage batteries,,'which consists insubjecting'the film's to a surface oxidation and in afterwardssubjecting the films to hydrogen in the presence of heat to reduce theoxid' to the metallic state, substantially asset forth. 1 1

5. The process of treating insoluble metallic films for admixture withthe active material for storage batteries, which consists in subjectingthe films to a surface oxidation, in then reducing the oxidizedsurface'to the metallic state, and in finally removing anymetallicimpurity present in the reduced surface, substantially as and for the 6.The process of treating insoluble metallic films for admixture with theactive material of storage batteries, which consists in subjecting thefilms to a surface oxidation, in then reducing the oxidized surface tothe metallic state, and in finally treating the films with a dilute acidto remove the metallic im urities present, substantially as and for't epurposes set forth. Q

This s ecification signed and witnessed this 4th ay of F'eby., 1908.

THOS. A. EDISON.

Witnesses:

ANNA R. KLEHM, FRANK L. Dyna.

